This invention relates to pump dispensers, of the kind having a pump module mounted on a container of a flowable product to be dispensed.
In a conventional dispenser pump the basic functional elements are a pump chamber of variable volume, having an inlet from the container and an outlet to a discharge opening, and an actuator operable to change the volume of the pump chamber to draw product into the pump chamber and expel the product through the discharge opening. At least the inlet and often also the outlet generally have one-way valves for efficient action. The simplest and cheapest pumps are movable-nozzle piston-and-cylinder pumps in which a reciprocable plunger carries a piston which works in a cylinder defined by a body of the pump and which fixes onto the container neck. Usually a ball valve is provided for the inlet, and often for the outlet. A return spring acts between the pump body and plunger to urge the latter to its extended position, automatically re-filling the pump chamber after each dispensing stroke.
While these pumps are reliable and effective, they usually use metal for the pump springs and often for the ball valves, making recycling difficult. In the simplest designs the metal also contacts the product which may be undesirable.
Over the years there have been many proposals for avoiding the use of metal in pumps. Deformable pump chambers, typically using bellows constructions and/or elastomer or thermoplastic elastomer materials, have been proposed and used. However these materials are expensive as well as usually non-recyclable, while bellows-form chambers are seldom effective.
U.S. Pat. No. 4,867,347 proposed a pump chamber having a resiliently restorable flexible wall which could be made from standard plastics such as polypropylene. Restoring force is provided by a special form of the flexible wall, comprising at least one facet having a concave boundary and a curved surface portion interrupting the facet to induce bending thereof in the dispensing stroke, this bending producing a strong restoring force tending to restore the flexible wall to the rest condition. The curved surface portion—typically a cylindrical surface portion—is axially inclined to the facet and meets it along the concave boundary. In the preferred form the flexible wall has the shape of a polygonal pyramid with plural facets. This structure has the advantage that it can be molded integrally with adjacent components, such as thicker portions for guiding the movement or mounting the flexible wall. However the restoring force achieved is often inadequate and the design did not become commercially used.
Here we propose novel forms of pump dispenser addressing the above issues.